The present invention relates generally to presses for shaping and curing tires. More particularly, the present invention relates to apparatus for positioning an uncured tire relative to a press for shaping and curing tires wherein the uncured tire is positioned and manipulated by a unique bag control or center mechanism configuration. More specifically, the present invention relates to a center mechanism which is highly versatile in terms of being adapted for optimum performance in different types of tire curing presses and for shaping and curing tires of differing sizes and configurations.
Numerous types of presses for shaping and curing tires have been developed over the years. One major construction feature of such presses is the mechanism for actuating the upper and lower mold sections for opening and closing the press to permit removal of a cured tire and insertion of an uncured tire on the one hand and the controlled pressurizing and heating of the tires within the mold sections on the other hand. In this respect, successful mechanisms for opening and closing presses have been developed that feature both mechanical and hydraulic actuation.
Another significant feature of such tire curing presses is the center mechanism, which provides the primary interaction between the press and a tire band being processed by the press, particularly during the manipulations of loading and unloading tires into the press. While various types of center mechanisms have been developed over the years, the most universally accepted have employed a flexible, generally cylindrical bladder or bag member that is secured to the press and that is capable of manipulation to be inserted within a tire band, radially distended in order to apply shaping pressure and curing pressure and heat to the interior of the tire band, and to strip the bladder from the tire after the curing process is completed. The factors involved in operation of a center mechanism bladder in conjunction with conventional bias-ply tires was relatively simple due to the cylindrical form of the uncured tire. With the wide acceptance of radial-ply tires, bladder manipulations assumed more complex and significant implications. Since uncured or green radial tire carcasses must be at least partially preformed before the breaker ply is positioned and affixed, the bead portions are, therefore, necessarily in closer axial proximity to each other in that the preformed tire band approximates, to a substantial extent, the configuration of the cured tire, as contrasted with the substantially cylindrical uncured configuration of a conventional bias-ply tire. As a result, the bead-to-bead dimension interiorly of a preformed radial tire substantially exceeds the axial distance between the beads. Therefore, a bladder or bag that has an axial extent that approximates the bead-to-bead dimension interiorly of a tire will, when axially upwardly extended to receive the tire, project a substantial distance above the upper bead of the tire. In such instances, movement of the upper and lower bead area of a bladder, together with control of the internal pressure, are significant in accurately concentrically locating the bladder within the tire to complete shaping and perform curing of a green radial tire band.
Center mechanisms employing a generally cylindrical bag or bladder member have assumed many forms in the commercial environment; however, it has been realized in recent years that the configuration of the bladder and its accuracy of placement within an uncured tire band are highly significant to the uniformity and, therefore, performance of the resultant cured tire. Many center mechanisms have inherent weaknesses or disadvantages based solely upon the construction of the bag or bladder and the manner in which it is attached to and manipulated by components of a center mechanism. For example, a bladder that is not symmetrical about both horizontal and vertical axes can readily lead to a lack of uniformity in the resultant tires. In instances where the bladder beads are fixed, the girth of the bladder is limited. In bladders having fixed beads at one end and a free end of the bladder, there is necessarily poor control over the free end of the bladder during bladder insertion into the uncured tire band. Further, in some instances, large volumes of curing media are required due to the bladder and center mechanism configuration. Most prior-art center mechanisms that are currently in commercial use suffer from one or more of the above limitations.
One prior-art center mechanism that is not subject to the above-described disadvantages is the Bag-O-Matic(copyright) center mechanism, which has been sold by Applicant""s assignee for many years. These center mechanisms have a bladder that has symmetrical construction around both the horizontal and vertical axes to achieve the resultant quality and uniformity of tires. In addition, the center mechanism is capable of sizing the bladder to the bead diameter of tires being cured. This minimizes the unsupported bladder between the tire bead and the bladder clamp rings, thus eliminating the problems associated with variance in the stretch of unsupported areas of the bladder and the consequent effect on tire uniformity, particularly in the bead areas of the tires.
Possible disadvantages of the Bag-O-Matic(copyright) center mechanism involve the potential mixing of operating fluid for the bladder manipulation cylinder with the cure media in the bag or bladder. With cure media on one side of piston rod seals and hydraulic operating fluid, classically water, on the other side heat transferred to the seals from the curing media severely affect seal life and that of related mechanical components, even though made from high-cost customized materials. In instances where a gas-curing media is employed, these areas of concern are intensified. The center mechanisms have also required spacers to set up stack and stretch heights for the bag or bladder, thereby providing potential for error on an operator""s part by selecting an improper spacer for a particular size. Thus, existing center mechanisms have all involved at least an extent of built-in or potential disadvantages that can materially affect tire quality and uniformity.
Therefore, an object of the present invention is to provide a tire curing press center mechanism having the capability of producing uniform, high-quality radial-ply tires. Another object of the invention is to provide such a press center mechanism that is capable of operating in conjunction with a wide variety of existing tire-loading and unloading devices without the necessity for alterations or modifications. A further object of the present invention is to provide such a press center mechanism that is capable of installation and use in a variety of existing presses, including both mechanical and hydraulic press designs that are currently utilized in the industry.
Another object of the present invention is to provide a tire curing press center mechanism that employs a bladder that is of symmetrical construction around both the horizontal and vertical axes. Yet a further object of the invention is to provide such a press center mechanism that is capable of sizing the bladder to accommodate differing bead diameters to thereby minimize the unsupported bladder area between the tire beads and the clamp rings for the bladder bead areas. Another object of the invention is to provide a tire press center mechanism that fully maintains these and other advantages of a conventional Bag-O-Matic(copyright) center mechanism.
Yet another object of the present invention is to provide a tire curing press center mechanism that eliminates possible disadvantageous features of a conventional Bag-O-Matic(copyright) center mechanism. Another object of the present invention is to provide such a center mechanism wherein the curing medium and the operating fluids for the center mechanism cylinders are completely separated, with individual optimumly designed seals maintaining the fluids within their operating components. Another object of the invention is to provide such a center mechanism wherein the curing media and operating media are physically spaced a substantial distance to preclude the transfer of heat from the curing media into the cylinder operating fluid. Yet a further object of the invention is to provide such a tire curing press wherein a cooling fluid may be circulated through the components joining the bladder containing the curing media and the cylinders containing operating fluid for manipulating the center mechanism components. Yet a further object of the invention is to provide such a center mechanism that eliminates operator error in misadjustment of stacking height, since the stacking height set-up may remain the same for all tire sizes unless it is desired to change the position of the bladder in relation to the top bead of the tires.
A further object of the invention is to provide a tire curing press center mechanism that employs commercially available cylinder technology. Yet a further object of the invention is to provide such a center mechanism that accommodates usage of cylinder operating fluids such as oil or water-glycol systems, where higher pressures can be readily utilized. Yet another object of the invention is to provide such a center mechanism wherein usage of higher pressure operating media for the cylinders permits the utilization of smaller cylinders and other components while providing the necessary actuating forces for manipulating the center mechanism components.
In general, the present invention contemplates a tire curing apparatus for manipulating a bladder relative to a tire in a tire curing press including, a lower plate ring for carrying a lower bead of the bladder, an upper plate ring for carrying an upper bead of the bladder, a first cylinder mechanism for selectively moving the lower plate ring and the upper plate ring, a piston rod attached to the upper plate ring and extending through the lower plate ring, a second cylinder mechanism located within the first cylinder mechanism for selectively actuating the piston rod to move the upper plate ring relative to the lower plate ring, a stretch-height control mechanism for controlling the position of the upper plate ring relative to the lower plate ring upon actuation of the second cylinder, and a bladder detector mechanism for positioning the upper plate ring at a predetermined position relative to a tire in the tire curing press.